Force | Wind Speed | Descrip-
tion | Sea Conditions | Wave
Hight Feet |
Force 0 | Less than 1 knot | Calm | Sea like a mirror. | 0 |
Force 1 | 1-3 knots | Light Air | Ripples with the appearance of scales;no foam crests. | 1/4 |
Force 2 | 4-6 knots | Light Breeze | Short, small-pronounced wavelets. | 1/2 |
Force 3 | 7-10 knots | Gentle Breeze | Large wavelets with some crests. | 2 |
Force 4 | 11-16 knots | Moderate Breeze | Increasingly longer small waves; some with whitecaps (foam crests). | 4 |
Force 5 | 17-21 knots | Fresh Breeze | Moderate lengthening waves, with many whitecaps and some spray. | 6 |
Force 6 | 22-27 knots | Strong Breeze | Large waves, extensive whitecaps, and some spray. | 10 |
Force 7 | 28-33 knots | Near Gale | Heaps of waves, with some breakers whose foam is blown downwind in streaks. | 14 |
Force 8 | 34-40 knots | Gale | Moderately high waves of increasing length and edges of crests breaking into spindrift (heavy spray). Foam is blown downwind in well-marked streaks. | 18 |
Force 9 | 41-47 knots | Strong Gale | High waves with dense foam streakes and some crests rolling over. Spray reduces visibility. | 23 |
Force 10 | 48-55 knots | Storm | Very high waves with long, overhanging crests. | 29 |
Force 11 | 56-63 knots | Violent Storm | Exceptionally high waves that may obscure medium size ones. | 37 |
Force 12 | 64-71 knots | Hurricane | The air is filled with foam and spray, and the 45ft sea is completely white | 45 |